The invention is directed to anisotropic polymers of liquid crystalline diepoxide and liquid crystalline diisocyanate and to a process for the production of these anisotropic polymers, possibly in the presence of catalysts, additional comonomers and other conventional additives.
Reaction products of bifunctional isocyanates and epoxies are known. They are usually designated as poly(isocyanurate oxazolidinones). It is also known that cyclotrimerization of isocyanates at lower temperatures first yields isocyanurate units which react with epoxy groups to form 5-membered oxazolidinone heterocycles only at elevated temperatures.
EP-A-0 252 359 describes the conversion of4,4'-diisocyanatophenyl benzoate with 4-epoxypropoxybenzoic acid 4'-epoxypropoxyphenyl ester. The reaction product is opaque. It has no liquid crystalline phase textures and contains only crystallized reaction products. It is stated in EP-A-0 252 359 that anisotropic polymers occur by reaction of various monomers only when the reaction temperature lies within the liquid crystalline range of the educts.
Diepoxides with mesogenic properties are described in various published references. For example, it is known that mesogenic diepoxides yield polymers with optical anisotropy when converted with various reacting agents and also when homopolymerized. Japanese Patents 63-10617 (1988) and 58-206579 (1983) describe the synthesis of various triaromatic bisazomethine diglyceridyl ethers and -esters. "Synthesis, Characterization and Theory of Polymeric Networks and Gels", Ed. S. M. Ahorni, Plenum Press, New York 1992, p. 147, describes the preparation of polyepoxy networks from mesogenic diepoxides having liquid crystalline properties. The diaromatic and triaromatic diepoxides used have broad 1 c phases. Diisocyanates with liquid crystalline properties are also known (e.g., W. Mormann, M. Brahm, Polymer 43, 187 (1993)). Cyclotrimers of mesogenic, diaromatic monoisocyanates have very weakly expressed 1 c properties as compared to the monomeric educts. Normally, the liquid crystalline character is lost during the cyclotrimerization reaction.